1. Field of the Invention
The present invention relates to an apparatus for controlling a compressor, a heat exchanger for evaporation, and a heat exchanger for condensation in a refrigeration cycle constituting a refrigerating air conditioner and a method of controlling the refrigeration cycle.
2. Discussion of Background
FIG. 14 schematically shows a refrigeration circuit of a conventional multi-chamber type air conditioner disclosed in JP-A-8-2534926. In FIG. 14, numerical reference 31 designates an outdoor unit; numerical reference 32 designates a variable capacity compressor; numerical reference 33 designates a four-way valve; numerical reference 34 designates an outdoor heat exchanger; numerical reference 37 designates a distributor; numerical references 41a through 41c designate three indoor units; numerical references 42a through 42c designate indoor electronic expansion valves; numerical references 43a through 43c designate electromagnetic switching valves; numerical references 44a through 44c designate electromagnetic switching valves; numerical reference 45 designates a controller; numerical reference 46 designates an outdoor blower; numerical reference 47 designates an electronic expansion valve; numerical references 48a through 48c designate indoor heat exchangers; numerical reference 49 designates a gas-liquid separator; numerical references 51 and 52 designate connection pipes for connecting the outdoor unit 31 to the distributor 37; numerical reference 53 designates a high-pressure pipe in the distributor 37; numerical reference 54 designates a low-pressure pipe in the distributor 37; numerical reference 55 designates an intermediate pressure pipe; numerical reference 56 designates a four-way valve; numerical reference 57 designates an accumulator; numerical reference 58 designates a pressure detector for a high pressure; and numerical reference 59 designates a pressure detector for a low pressure.
The distributor 37 and each of the indoor units 41a through 41c are connected by two pipes. The indoor units 41a through 41c are composed of the indoor heat exchangers 48a through 48c and the electronic expansion valves 42a through 42c, wherein the electronic expansion valves 42a through 42c are connected to the intermediate pressure pipe 55, and the indoor heat exchangers 48a through 48c are connected to the low-pressure pipe 54 and the high-pressure pipe 53 through the electromagnetic switching valves 43a through 43c and 44a through 44c. Further, the pressure detectors 58 and 59 are installed in the outdoor unit 31, wherein detection signals from the pressure detectors are inputted in the controller 45. The controller 45 controls a capability of exchanging heat between a refrigerant circulating in piping and the outdoor heat exchanger 34 using the compressor 32, the four-way valve 33, and the blower 46.
In the next, operation will be described. A case that the indoor unit 41a is in a heating mode and the indoor units 41b and 41c in a cooling mode will be described. A high-temperature high-pressure gas refrigerant compressed by the compressor 32 passes through the four-way valve 33 and is partially condensed by the outdoor heat exchanger 34 to be transformed into a two-phase refrigerant. Thereafter, the refrigerant passes through the high-pressure connection pipe 51 and flows into the distributor 37 located in a room.
The two-phase refrigerant in the distributor 37 passes through the four-way valve 56 and is separated into a gas and a liquid by the gas-liquid separator 49. Thus obtained high-pressure gas refrigerant flows into the indoor unit 41a through the electronic switching valve 44a, and dissipates heat to be condensed by the indoor heat exchanger 48a. Thereafter, the refrigerant flows into the intermediate pressure pipe 55 through the electronic expansion valve 42a and joins with a liquid refrigerant flowing into the intermediate pressure pipe. from a liquid-phase portion through the electronic expansion valve 47 and flows into the indoor units 41b and 41c. In the indoor units 41b and 41c, the refrigerant is respectively changed to have a low pressure by the electronic expansion valves 42b and 42c and is endothermically evaporated by the indoor heat exchangers 48b and 48c. Thereafter, it joins with the low-pressure pipe 54 through the electromagnetic switching valves 43b and 43c. Further, it passes through the four-way valve 56 and circulates by passing through the low-pressure connection pipe 52, the four-way valve 33, and the accumulator 57 and returning to the compressor 32. As described, a refrigeration circuit for simultaneously heating and cooling, in which a cooling operation is conducted in the indoor heat exchanger 48a and a heating operation is conducted in the indoor heat exchangers 48b and 48c, is realized.
In the above refrigeration circuit, a high pressure discharged from the compressor 32 and a low pressure sucked by the compressor 32 are detected by the pressure detector 58 provided in the high-pressure pipe in the outdoor unit 31 and the pressure detector 59 provided in the low-pressure pipe, and the result of this detection is transmitted to the controller 45. The controller 45 compares each detected value respectively with preset high-pressure or low-pressure target value after receiving signals transmitted from the detectors 58 and, 59. Further, the controller 45 calculates a requisite capacity of the compressor 32 based on a result of this comparison and a requisite capacity of the outdoor heat exchanger 34 based on a result of this calculation. Further, the controller 45 controls a capacity of compressor 32 based on the result of this calculation and simultaneously controls a capability of exchanging heat in the outdoor heat exchanger 34 by adjusting the revolutional numbers of the blower 46.
Further, when a variation of a load is estimated large, a capacity of the compressor 32 and a capacity of the outdoor heat exchanger 34 are controlled and simultaneously the four-way valve 33 is switched based on determination of whether or not the outdoor heat exchanger 34 is used as a condenser of heat dissipator or as an evaporator of heat absorber from the result of calculation, whereby a drastic variation of the load is managed.
By such a control, it is possible to deal with changes of a load on an outdoor unit side in response to environmental conditions of weather and a climate, opening and closing of side doors of the indoor units 41a through 41c, a change of a preset indoor temperature, and a change of the load of the indoor unit caused by switching between cooling and heating modes.
In controlling thus constructed conventional multi-chamber type air conditioner, the high-pressure target value and the low-pressure target value necessary for calculating a degree of controlling the compressor, of the outdoor heat exchanger, and of the four-way valve were fixedly preset in designing the refrigeration cycle and were constant regardless of a preset value of indoor air temperature and an outdoor air temperature.
Specifically, the high-pressure target value and the low-pressure target value were set so as to be able to deal with a large load for obtaining a general purpose apparatus which can deal with any load.
Since the method of controlling the conventional multi-chamber type air conditioner had the above-mentioned structure and operation, the air conditioner was not always energy-saving as a whole as long as the capability for exchanging heat of the indoor heat exchangers 41a through 41c were not controlled by the controller 45 in the outdoor unit 31.
Further, energy consumption of the compressor 32, which occupied the largest ratio in the entire energy consumption of the air conditioner, was substantially constant irrespective of the preset value of indoor air temperature and an outdoor air temperature. For example, in case that the preset value of indoor air temperature was high or an outdoor air temperature was low at a time of cooling operation, it was possible to save energy. However, there was a problem that the energy was not sufficiently saved.
It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide an apparatus for controlling a refrigeration cycle and a method of controlling the refrigeration cycle, by which a proper capability of the refrigeration cycle can be quickly obtained under a running condition and the running condition can be controlled so as to save energy. For example, the object of the present invention is to obtain the apparatus of controlling the refrigeration cycle and the method of controlling the refrigeration cycle, by which a high-pressure detection value and a low-pressure detection value of the refrigeration cycle can be quickly converged in to a high-pressure target value and a low-pressure target value respectively under a running condition, and energy consumption of an entire air conditioner can be minimized within an allowable range for attaining a target under a running condition.
Another object of the present invention is to obtain an apparatus of controlling a refrigeration cycle and a method of controlling the refrigeration cycle, by which a high-pressure target value and a low-pressure target value used for converging into a preset temperature in a heat exchanger on a user side and a control for assuring a capability can be automatically set and properly changed in response to running conditions.
According to a first aspect of the present invention, there is provided an apparatus for controlling a refrigeration cycle of circulating a refrigerant in a compressor, a heat exchanger for condensation, a flow rate control valve, and a heat exchanger for evaporation, connected each other, comprising: a first means for changing a capability of exchanging heat of the heat exchanger for condensation, a second means for changing a capability for exchanging heat of the heat exchanger for evaporation, a means for operating a running capacity of the compressor, and a control means for reducing a difference between a running condition of the refrigeration cycle on a high pressure side or a low pressure side and a target.
According to a second aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle, wherein the control means works to minimize a consumption energy in the smallest one of the differences between the running condition on the high pressure side or the low pressure side and the target.
According to a third aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle, wherein the control means works to make a difference between an inlet temperature and an outlet temperature of a heat exchanging fluid of a heat exchanger on a user side, being one of the heat exchanger for condensation and the heat exchanger for evaporation, to reach or approach to a target of temperature difference.
According to a fourth aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle, wherein the running condition on the high pressure side of the refrigeration cycle is under a discharge pressure of the compressor or a saturation temperature corresponding to this discharge pressure; and the running condition on the low pressure side of the refrigeration cycle is under a suction pressure of the compressor or a saturation temperature corresponding to this suction pressure.
According to a fifth aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle, wherein the running condition on the high pressure side of the refrigeration cycle is under a condensation pressure of the condenser or a saturation temperature corresponding to this condensation pressure; and the running condition on the low pressure side of the refrigeration cycle is under an evaporation pressure of the evaporator or a saturation temperature corresponding to this evaporation pressure.
According to a sixth aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle, further comprising: a target value setting means for automatically setting one of target values of the running conditions on the low pressure side and the high pressure side of the refrigeration cycle in reference of a preset value of an inlet temperature or an outlet temperature of heat exchanging fluid in a heat exchanger on a user side and automatically setting the other of the target values in reference of a temperature of heat source.
According to a seventh aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle further comprising: a target value changing means for increasing or decreasing the target value on the low pressure side in reference of a relationship between the running condition on the low pressure side in a stable running condition of the refrigeration cycle and the target value on the low pressure side, wherein the heat exchanger for evaporation is the heat exchanger on the user side.
According to an eighth aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle further comprising: a target value changing means for increasing and decreasing the target value on the high pressure side in reference of a relationship between the running condition on the high pressure side in a stable running condition of the refrigeration cycle and the target value on the high pressure side, wherein the heat exchanger for condensation is the heat exchanger on the user side.
According to a ninth aspect of the present invention, there is provided the apparatus for controlling the refrigeration cycle, wherein the target value changing means increases and decreases the target value on the high pressure side or the low pressure side of the refrigeration cycle based on a relationship between the inlet temperature of the heat exchanging fluid in the heat exchanger on the user side in a stable running condition and the target value, and on a relationship between the outlet temperature of the heat exchanging fluid in the heat exchanger on the user side and the target value.
According to a tenth aspect of the present invention, there is provided a method of controlling a refrigeration cycle comprising: a step of making a parameter of degree of change from various capacities in a compressor based on changes of running conditions on a high pressure side or a low pressure side of the refrigeration cycle in response to the degrees of change of the various capacities of the compressor, a step of obtaining standard degrees of change of capabilities for exchanging heat of heat exchangers for condensation and evaporation so as to make the capabilities for exchanging heat be target values in the running condition on the high pressure side and the low pressure side of the refrigeration cycle by varying the capabilities for exchanging heat with respect to the degrees of change of the various capacities of the compressor, made as the parameter, a step of producing a plurality of degrees of change based on the obtained standard degrees of change, a step of operating the plurality of degrees of change when the plurality of degree of change of the heat exchangers for condensation and evaporation respectively make the capabilities of the heat exchangers to exceed their allowable capabilities for exchanging heat so that the plurality of degrees of change makes the capabilities involved within their allowable capabilities for exchanging heat, and a step of selecting degrees of change among the plurality of degrees of change of the capabilities for exchanging heat obtained with respect to the parameter, which degrees of change make the capabilities of exchanging heat to approach to the target value of the running condition on the high pressure side or the low pressure side.
According to an eleventh aspect of the present invention, there is provided a method of controlling a refrigeration cycle comprising: a step of operating degrees of change making a running capacity of compressor and throughput capacities of heat exchangers for condensation and evaporation to approach to a target on a low pressure side or a high pressure side by changing the running capacity of compressor and the throughput capacities of heat exchangers for condensation evaporation using a difference between the target on the low pressure or high pressure side and a current running condition, and a step of selecting degrees of change making the running capacity and the throughput capacities to maximally approach to the target on the low pressure or high pressure side among the degrees of change.
According to a twelfth aspect of the present invention, there is provided the method of controlling the refrigeration cycle, further comprising: a step of selecting a combination of the degrees of change making a consumption energy minimize by controlling the degrees of change of the running capacity of the compressor and the degrees of change of the capabilities for exchanging heat in the heat exchangers for condensation and evaporation.